Heathkit Service Bulletins - Cont.
Joseph W Lutz
joelutz at JUNO.COM
Thu Jun 12 00:32:10 EDT 1997
Hi All,
Following is some more that I have pulled off the Fiche - enjoy!
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June 15, 1967
HW-12
Bulletin No.
80M SSB Transceiver VFO Drift
HW-12-1D
An incorrect shipment of coils has been included in a recent production
run of the HW-12, HW-22 & HW-32.
The coil Part Number is 52-25 & has a N-750 ceramic installed inside the
can...rather than a silver mica.
The mis-manufactured coil causes drifting in the circuit...which can be
corrected by replacing with a NO, 52-25 of proper construction. All
stock currently on hand in the parts dept is correctly manufactured.
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April 15, 1968
HW-12
Bulletin No:
80M SSB Transceiver IF Feedback in Receive Mode
HW-12-2D
R-121 may be changed from 12K ohm to 22K ohm 2W (Part NO. 1-11-2) to stop
IF feedback in receive operation.
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April 18, 1968
HW-12
Bulletin No:
80M SSB Transceiver IF Oscillating
HW-12-3D
DELETE: (2) I-16 (5) RESISTOR, 4.7K OHM
ADD : (2) I-16 (6) RESISTOR, 4.7K OHM
DELETE: (2) I-22 (5) RESISTOR, 22K OHM
ADD : (2) I-22 (4) RESISTOR, 22K OHM
DELETE: (4) 83-69-4 (1) CIRCUIT BOARD, 85-69 SCREENED
ADD : (4) 85-69-9 (1) CIRCUIT BOARD, 85-69 SCREENED
NOTE: (R91) will reduce action of the S-Meter.
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September 26,
1968
HW-16
Bulletin No:
Novice Transmitter Side Tone
HW-16-1
When using the HW-16 with a VFO sometime a partial operation of the
sidetone oscillator takes place due to an increased loading on the bias
voltage. This can be corrected by changing R-69 from a 120K hom resistor
to a 220K ohm resistor (PN 1-29). Also, the original schematic shows
R-16 as a 4700 ohm resistor which is incorrect. R-16 should be shown as
a 5600 ohm resistor.
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May 23, 1974
SB-100 Diode leakage in the SB-100, SB-101, HW-100
Bulletin No:
SSB Transceiver
SB-100-1
The silicon diodes used in the SB100 & SB101 are standard power diodes
rated at 500PIV & 750MA. For each condition described, the diodes should
be replaced with an equal value to maintain proper opration.
1. Diodes D902 & D903, when leaky, will have an effect on ALC
indication. The ALC indication will be normal for the first half hour to
an hour. Then the meter indication will start dropping off until there
is very little indication.
2. D101, when leaky or defective, will cause slow or no receiver
recovery after transmitting for any period of time.
3. D905, under leaky conditions, will cause very slow or no receiver
recovery and false meter indications. The meter will kick up scale &
slowly drift down to zero.
4. D201 will result in a decrease in VOX sensitivity to the point where
the VOX circuit will not be activated. It can also result in increasing
VOX delay, causing the relay to stay in the transmit condition.
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May 23, 1974
SB-100 Alternate Method of Neutralizing The Final
Bulletin No:
SSB Transceiver Amplifiers
SB-100-2
1. Disconect final plates & screen grid.***
2. Turn unit on.
3. Rotate the BAND switch to 28.5.
4. Place the VTVM RF probe in the ANTENNA connector.**
5. Set the FUNCTION switch to TUNE.
6. Rotate the LEVEL control fully clockwise.
7. Adjust the PRESELECTOR control for a maximum reading on the VTVM.
8. Adjust the FINAL control for a maximum indication on the VTVM, with
the LOAD control set at the 50 ohm position.
9. Using an insulated screwdriver, adjust neutralizing capacitor for a
MINIMUM indication on the VTVM.
10. Readjust the neutralizing capacitor for a minimum indication on the
VTVM.
11. Turn the FUNCTION switch to the off position.
12. Discharge high voltage power supply capacitors.
13. Reconnect final plates & screen grid.
**VTVM & RF probe will be needed.
***To remove screen voltage in SB-100, SB-101, HW-100 & HW-101 disconnect
R920 (100 ohm resistor) from buss wire between pins of V8 & V9. In the
SB-102 removeal of accessory plug is all that's required. To remove high
voltage in SB-100, SB-101 & SB-102 disconnect red wire at lug 4 (in
Sb-100 lug 3) of terminal strip BK that goes to grommet BL. In HW100 &
HW101 disconnect red wire going to lug 1 of RF choke in final cage.
NOTE: Take adequate steps to eliminate any possible contact with B+ or
B+ shorts to chassis after disconnecting wire & resistor.
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Okay gang - it's past midnight and I just finished watching game 5 of NBA
playoffs and ran up to type in between of periods, etc. Time for nite -
nite. More to follow, and as stated before - any specific Heathkit SVC
Bulletins you would like please let me know and I will check fiche for
same and pull them off. FYI: The fiche contains everything manufactured
by Heathkit during the aforementioned time period. Ciao!
73 de JOE
- - - - - - - - - - -W7LPF/4 (NNN0KUU)- - - - - - - - - - - - - - -
QWCA - NCVA - SOWP - FISTS
Gordonsville, Va 22942 (Orange County)
Looking for: Heathkit HR/HX-20, MR/MT-1,
Collins 516F-2, 312B-4, EFJ TR Switch
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